Rain helps in short term, but fire risk remains high

Hillsides in San Diego County quickly turned from green to brown in April after a mid-month hot spell.

Hillsides in San Diego County quickly turned from green to brown in April after a mid-month hot spell. (Robert Krier San Diego Union-Tribune)

Robert Krier

Rain this week, coming after an exceptionally dry winter and April, should give a boost to backyard gardeners and provide a brief reprieve from what has become an almost omnipresent wildfire danger in the San Diego County.

But the rain in early May should prove too little, too late to prevent another bad fire season as the year progresses, fire experts say.

“We get into an endless cycle of ‘the worst fire season ever,’ ” said San Diego Fire-Rescue Battalion Chief John Fisher. “I don’t want to paint that picture, because it depends on what happens later in the year.

“But it’s extremely dry out there. Everyone is in agreement — it’s going to be a very bad year.”

The May rain, the first appreciable precipitation in the region in six weeks, is welcome but not nearly as valuable to back country and backyard vegetation as winter rains. The longer daylight hours in May and the higher sun angle make it harder for plants to soak up the moisture before it evaporates.

And a quick warm up expected this weekend, when inland temperatures could climb back up to 90 degrees, will further speed up the evaporation.

Alex Tardy, a meteorologist at the National Weather Service’s Ranch Bernardo office, said this week’s rains could make grasses pop up on some hillsides, but any benefits will be short-lived.

“For the trees, it’s already too late for them,” Tardy said. “Trees need the rain in December, January and February. Things are all out of whack.”

Fall and early winter this year, the start of San Diego’s rainy season, were the driest on record. The city recorded just 0.09 of an inch of rain from Oct. 1 to Jan. 7. Normally the city would get more than 3 inches of rain during that period.

That extremely dry stretch put unprecedented stress on native vegetation. Plant moisture reached the lowest levels ever recorded locally in December, when the Lilac fire spread quickly in North County and a swarm of wildfires ravaged both Northern and Southern California.

San Diego’s dry streak ended on Jan. 8, when 1.75 inches fell over three days. But the region fell back into far-below-normal rainfall for the rest of the winter, and the stresses on plants returned.

April was exceptionally dry, even with the tiny bit of rain on the last night of the month on Monday. The monthly total was just 0.02 of an inch — 0.76 of an inch below normal.

Through April 30, San Diego’s total of 3.2 inches was the second lowest rainfall on record for this late in the season. Only 2001-02, with 2.99 inches through the end of April, was drier.

Fire ignition risk

Shyh-Chin Chen, a meteorologist for the U.S. Forest Service who is studying fire and fuels at the Pacific Southwest Research Station in Riverside, said the scant rains the region received this spring have been sufficient to keep the chances of fire ignition low, in the short term.

But the long-term picture does not look so rosy, he said. San Diego County hasn’t had any massive, back country wildfires since 2007, and plenty of dead vegetation has built up on the hillsides and in the canyons.

“The available fuel is out there,” Chen said. “We’re just waiting for the right weather conditions to ignite those fuels.”

From a fire standpoint, that means winds. In May 2014, record-breaking heat, coming in the middle of a drought, accompanied strong Santa Ana winds in San Diego County. A series of fires that month, including the Cocos fire in San Marcos, caused nearly $30 million in property damage in the area.

Before this week’s rains, conditions were very dry in the county’s open spaces, although not quite as dry as they were in May 2014. Hillside grasses this year quickly turned from green to brown after a mid-April heat spell, with temperatures in the mid 90s in many locations.

“Everything dried and died,” Tardy said.

In the backcountry, many chaparral plants are showing little or no new growth. Fisher said meager growth is a reflection not only of this exceptionally dry year, but of the previous dry years. The long-range drought pattern, interrupted only by the wet year in 2016-17, has left soil moisture depleted, which affects the plants.

“The plants are still alive, but they have a lot of dead wood,” Fisher said.

In the garden

The dry year has had a big impact in the garden, too.

“Our water demands for the fall and winter were off the charts,” said Sean Peer, who has worked at El Plantio Nursery in Escondido for 30 years.

In a normal winter, with cloudier skies and more rain, the nursery would need to water its inventory every Monday, Wednesday and Friday, Peer said.

“This winter was so dry, and there was so much sunshine, we had to water every day, which is crazy,” he said. “I even gave my natives a little extra water, which I never do.”

In February, customers brought in plant samples damaged after a strong Santa Ana. The wind damage was exacerbated by the dryness, he said.

Although the last month and a half have been very dry, many of the nights have been cool, and that has caused what Peer calls “cold wilt” on many warm-season plants. Many trees have also delayed their usual spring growth.

“Our sycamore is usually budding out in February. It’s just now budding,” Peer said. “A lot of people’s apricots and plums haven’t even popped out yet.